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Portable III keyboard error

N

Neosodium

Experienced Member
Joined
Nov 30, 2010
Messages
119
Location
Oxfordshire, UK
I fired up the Portable III today, only to find the machine reporting a keyboard error and then making a noise like one of the keys is being held down constantly. I disassembled the keyboard and it only stopped making the noise when I disconnected the cable at either end.

I hope one of the chips on the keyboard hasn't gone. It's an awful keyboard (why on earth did they make it like that?) but its the only one that clips in place over the screen :( is there any way to replace the 'guts' of the keyboard but not the case?
 
The problem seems to be worse than I thought, the machine does the same thing with a known good keyboard plugged in, and without one plugged it in it reports "system or keyboard failure" ... is my portable in dead system board territory?

I would be very grateful to anyone who can help me find a solution, as I don't think system boards for a portable III come easy or cheap.
 
Have you checked the cable inside the computer too?

There's a short cable that goes from the keyboard socket to the motherboard. It might have come unplugged somehow, or the cable might have deteriorated.
 
Have access to a multimeter/ohmmeter? I don't have experience with that particular system, but I would be tempted to test the keyboard cable from right on the keyboard pcb through to where it connects to the system board, to make sure that the cable had no internal issues and that the connectors were working cleanly. Just to be sure that it wasn't a cable or connector issue before going after the system board.
 
Thanks for the idea, i'll check the internal cable with a multimeter. I'm assuming that none of the pins/wires should be connected to eachother. Does anyone know what voltage should be present and what pin(s) it should be at on an AT socket?

if it wasnt for the fact that trying with a different keyboard made no difference, I'd have assumed the keyboard or its wire was the issue, which would be a lot easier to resolve than an internal problem. Fingers crossed one of the connectors is busted, not the keyboard circuitry on the system board.

Incidentally, it only beeps as if a key is being held down when a keyboard is plugged in, but it reports "keyboard or system unit failure" when one isn't, as opposed to just "keyboard error" when one is.

Are these known symptoms? I really don't want to have to give up on the Portable III, as I have wanted to own a working one for a long time.
 
Ok, I have checked the inner lead with the multimeter and that seems to be fine, but when checking the voltages at the connector, comparing with this page http://www.bbdsoft.com/keyboard.html pin 1 and 2 were +5v (they should be the clock and data pins respectively) Pin 5 did not show any voltage, despite pin 5 being the +5v pin and there was no ground on any of the pins (should be pin 4) - I used the case chassis as ground.

I checked these voltages with another AT socket and that showed the right voltages on the right pins. Something is quite wrong here. Anyone have any idea?
 
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